There are several information's of immense importance already given in the question. Based on those information's the answer can be easily deduced.
Initial number of bacteria in the culture = 1000
Number of bacteria after t hours = 1000 (2)^t
Then
1000 (2)^t = 50000
2 ^t = 50
t = 5.6
I hope the procedure is clear enough for you to understand.
Answer:
If the mitral valve doesn't close properly, systemic circulation will be affected.
Explanation:
There would be more hours of sunlight at the equator
Primary succession would most likely occur after a lava flow.